At present, along with the rapid development of a Wireless Local Area Network (WLAN) in the field of wireless networks, a demand for the coverage of the WLAN is growing, and a requirement on throughput is also increasing. In industrial standard group Institute of Electrical and Electronic Engineers 802.11 (IEEE802.11), a series of most common WLAN technical standards such as 802.11a, 802.11b and 802.11g are defined at first, and then other task groups dedicated to develop specifications related to technological improvements on conventional 802.11 appear one after another. For example, a 802.11n task group expresses a requirement on High Throughput (HT), introduces Multiple-Input Multiple-Out-put (MIMO) and beam-forming technologies, and supports a data rate as high as 600 Mbps; a 802.11ac task group further presents the concept of Very High Throughput (VHT), and introduces a higher-channel bandwidth technology, a higher-order MIMO technology, a Multiple-User MIMO (MU-MIMO) technology and the like to achieve a data rate capable of reaching more than 1 Gbps; and certainly, a new protocol is required to be backwards-compatible with a previous protocol.
In the WLAN, an Access Point (AP) and a plurality of STAB associated with the AP form a Basic Service Set (BSS). When a channel is shared by a plurality of STAB, it is difficult to detect a conflict in a wireless environment, and one major problem is a hidden STA. The hidden STA is specifically shown in FIG. 1, and FIG. 1 shows three BSSs, i.e. BSS1, BSS2 and BSS3, wherein STA A transmits data to STA B, STA C also transmits data to STA B at the same time, and the simultaneous data transmission of STA A and STA C may cause a conflict because STA C and STA A are located outside the coverage of each other. Therefore, from the point of STA A, STA C is a hidden STA. In order to solve the problem of hidden STA, 802.11 put forwards a virtual channel detection mechanism, that is, channel reservation time information is included in a frame header of a wireless frame, another guest STA receiving the wireless frame including the channel reservation time information sets a locally stored Network Allocation Vector (NAV) of which a value is set to be a maximum value of the channel reservation time information, and within the time, the guest STA will not transmit data, thereby avoiding a collision caused by the competition of a hidden node for a channel. The guest STA can transmit data only after the NAV is reduced to be zero. For example, a transmitter transmits a Request To Send (RTS) frame including the channel reservation time information for channel reservation, and a receiver responds with a Clear To Send (CTS) frame also including the channel reservation time information for channel reservation confirmation to ensure that the transmitter can finish frame switching. The setting of the NAV in the RTS/CTS frame is shown in FIG. 2.
In the WLAN, in order to better reduce power, when an STA detects a Physical Protocol Data Unit (PPDU) and a header of the PPDU indicates that the STA is not a receiver of the PPDU, the STA may give up receiving the PPDU and does not update own NAV. For example, in a WLAN protocol, the STA may give up receiving a certain PPDU and does not update own NAV under two conditions as follows:
the PPDU is a Single User (SU) VHT PPDU, and a Group Identifier (ID) and a Partial Application Identifier (AID) in its header indicate that the STA may not be a target receiver, that is, the Partial AID in the PPDU is different from a Partial AID of the STA, or the Group ID in the PPDU is 0, but the STA is neither an AP nor a Mesh STA; and
the PPDU is an MU VHT PPDU, the STA is not in an MU group indicated by the Group ID in the PPDU, or the STA is in the MU group indicated by the Group ID in the PPDU but a space-time stream number indicated at an MU group position where the STA is located is 0.
In a prior art, it is defined that a STA can drop a PPDU and does not update a NAV under a certain condition, but the subsequent operation of the STA is not specified, which may cause a transmission collision. For example, STA1 transmits a VHT PPDU to STA2, STA3 is a guest STA and can receive a signal of STA1 but cannot detect a signal of STA2, that is, STA2 and STA3 are mutually hidden STAB; STA3 determines that the PPDU is not intended to be transmitted to itself by detecting the header of the PPDU, selects to drop the PPDU, and does not update the NAV. After the VHT PPDU is transmitted, STA2 returns an Acknowledgement (ACK) frame to STA1 after a Short Inter-Frame Space (SIFS); STA3 may compete for a channel after the transmission of the PPDU is ended, wherein STA3 can know a transmission ending moment of the PPDU through the frame; and if STA3 competes for the channel by virtue of an Arbitration Inter-Frame Space[Access Category] (AIFS[AC]) or a Distributed Inter-Frame Space (DIFS) (which is generally shorter than the transmission time of the ACK frame), and since STA3 did not update own NAV and cannot detect the ACK frame transmitted by STA2, the signals of STA2 and STA3 are likely collided at STA1, that is, STA3 interferes in data transmission between STA1 and STA2. Similar conditions may occur in MU transmission and the like, and they will not be repeated.